Which style should I buy?

Every person has their own opinions about which style is the "best". Rather than point out a definitive list, I'll list the pros and cons of each style, and let you decide. It is easier, however, to get the newer styles. There is also a list of all CS songs and their appearances at Console Songs Guide.

Very small default songlist; only 39 songs by default. All other songs must be unlocked.

You need to pay a monthly fee to play the game (requires PASELI or a Japanese credit card).

Some songs cost additional PASELI to access, such as songs in the rarely appearing champion mode courses and song packs.

Some songs are locked for certain periods of time, and can't be accessed afterwards.

No EXPERT mode.

Song records only show EX score and miss count (same as the arcade).

Missing several custom options from the arcade games, such as PACEMAKER NEXT.

Which controller should I buy? I can't afford a controller right now, should I just play on a Dualshock?

Personally, I would wait to have the cash to buy one game and the controller at the same time. However, if you are -that- pressed for cash, I'm not stopping you from playing on a Dualshock. You won't get the same experience, however, and playing on a Dualshock is confusing as hell.

As far as buying controllers, there are a few options:

Konami Controller (JKOC) - An official controller by Konami, runs for about $90 from most online retailers. The keys are spaced correctly, but the turntable is smaller and closer to the keys. The keys are switchable so that you can emulate both the first and second player sides. People have problems with sticky keys, but you can mod your controller using cardboard to get around these problems.

American Controller (KOC) - Also made by Konami, this controller comes bundled with the American beatmania. These controllers used to retail for about $50, but nowadays they can be tricky to obtain depending on where you live. Since it was made and sold in the US it's easier to obtain there, but if you're importing to Europe expect to pay $100 or more. It has some slight differences from the Japanese controller mentioned above; most are cosmetic, but it is worth noting that the buttons are significantly redesigned and the traditional "plunger" design has been completely replaced, and are therefore much less prone to sticking. This controller is leaps and bounds better than an unmodded KOC, though KOCs can more easily be modded to a player's exact preference in terms of key travel distance by adding or removing layers of cardboard. Though it comes bundled with the American beatmania, this controller is fully compatible with the Japanese versions of IIDX.

Third-Party DJ Dao ASC - A Chinese manufacturer of various Bemani controllers sells several editions of IIDX controllers. High quality arcade feel controllers that are customizable to be arcade perfect. As of 2008, the product line consists of: A smaller controller, resembling a larger KOC with lights and arcade feel ($300 shipped), A larger controller, resembling a KASC with lights and arcade feel ($400 shipped), and an enormous arcade-perfect doubles deck ($1000 shipped). Independent overseas seller makes some people nervous, shipping is brutal, wait can take a week to a month, quality is excellent.

Konami ASC - The official arcade-style controller by Konami. It's huge, it's pricey, and for some, it's worth it. The price tag is quite hefty, but with arcade perfect dimensions, clicking keys, and switchable from first player to 2nd player, lots of people have purchased them. Expect to pay around $350-400 when all is said and done.

Rave Discman - Don't buy one. The price is attractive, but frankly, it's not all that great. For one, the keys are the wrong shape and are not spaced correctly. It's better to hold out for a Konami controller. It's possible to use a Rave Discman as a base for your own ASC, which some people on the forums have done. Take note this controller also has some voltage issues which could fry PS2->USB convertors that you might use.

Third-Party US ASC - two US controller makers well-known in the Pop'n Music community have both started producing ASC-like controllers for IIDX. These manufacturers are known for having long production times, good playability, and reasonable prices. Note: As of 2008, DA is not accepting new orders, and Ransai is only accepting replacements from people selling their place in the order queue.

There's a port on the side of my beatmania IIDX controller and I can't fit my finger in there? What is it for?

The port is meant for a foot pedal for beatmania III, but no home versions of beatmania III have been made. You can plug in a pedal from the drummania home controller into it, and triggering the pedal acts as a scratch. Cool, but mostly pointless.